DirectMusic Technology

The establishment of the MIDI protocol in 1982 enabled independent composers to effectively control the entire recording process from home-based studios and contributed significantly to the sound of the 1980s – from sequenced industrial mixes to lush electronic soundtracks. Its contribution was marred by an imprecise timbral definition that can occur when MIDI files are played back on random sound cards. As the 1990s got underway, sampling technology became widespread and created two distinct directions for composers to follow. On one hand, it gave composers the ability to create richly layered digital recordings of acoustic and electronic instruments. On the other, it promoted a kind of creative thievery, where composers borrowed the licks and grooves of previously recorded artists to create new compositions.

Several formats that support sampling technology are available on the PC. The most common of these is the wave (WAV) format, which makes possible the high-bandwidth digital rendering of sound. A weakness of the wave file format has been the lack of a standard for the economical delivery of musical performances – and this is where DirectMusic comes in. Combining MIDI, support for hardware acceleration and software synthesis, and an integrated delivery system for custom samples, DirectMusic provides an economical means of delivering professional quality musical performances, addressing difficult timing issues with features such as buffered, time-stamped events and a global time reference.

One of the most powerful aspects of DirectMusic is its full implementation – as part of DirectX 6 – of the industry-ratified downloadable sounds (DLS) specification. In the past, it was impossible to get consistent playback with MIDI and performance quality varied depending on the sound card or playback device. DLS allows software developers to add sound samples to the General MIDI (GM) patch set of a wavetable synthesiser and has applicability both to the games developer and the musician. For example, it would allow the former to include a digital recording of a tyrannosaurus’ roar and have it associated with a specific instrument number within a wavetable synthesiser. Within the music realm, it allows the creation of custom sounds based on actual recordings of instruments. More generally, a DLS sample can essentially hold any sound, including spoken dialogue.

DLS collections are based on wave files – which can contain a single note, a musical phrase, a sound effect, dialogue, or anything else – and allow the composer to specify the exact timbres desired. The result is that they will get precise timbral definition in their scores – and what users hear in their products is exactly what the composer created in their studio. Using DLS wave files can be imported into a collection and manipulated in the same way that MIDI controllers manipulate any synthesised sound source and because DirectMusic features the compression of wave files within DLS collections, their use is more viable than ever.

In addition, DirectMusic supports two methods of synthesis: hardware synthesis, in which the sound card uses MIDI events to create the audio heard through a PC’s speakers, and software synthesis, in which the CPU itself creates the audio waveform. The DirectMusic software synthesiser acts like a sampler inside the user’s PC. Thanks to the software synthesiser, most users will hear scores that are created entirely inside the CPU itself and played back much like a recording of a performance. However, in those cases where a sound card provides capabilities beyond the software synthesiser, DirectMusic can use the sound card instead. That way, DirectMusic provides the best of both worlds: the excellent fidelity of the wave format and the compactness, flexibility, and interactivity of MIDI.

DirectX 8’s integration of DirectSound and DirectMusic into the DirectX Audio component paves the way for the processing of synthesised music fragments in the same way as normal audio tracks. The support of DLS2 (Downloadable Sounds Level 2) standard has made it possible to apply effects designed originally for synthesised (MIDI) music – such as reverb – onto standard sound files of WAV format. With DirectX 8, users can synthesise sound, mix it with normal audio tracks and then process the unified track within a common 3D audio interface.

Audio Scripting is another new feature introduced with DirectX 8. This gives the sound designer a great deal more control – independent of programming complexities – over how a game’s sound accompaniment is processed and how the sound responds to interactive inputs which themselves depends on the precise conduct of the game.

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